1. Field of the Invention
This invention relates to a jack extension tube for use on power seat adjuster mechanisms for vehicles and, in particular, to a jack extension tube having low-noise operational characteristics and a low-torque internal stop-release.
2. Description of Related Art
Jack extension tubes are used in power seat adjuster mechanisms for vehicles to operably connect a vehicle seat track or seat back to a powering mechanism to move the seat or any component thereof in a desired direction via a link member. By varying the length of the tube, jack extension tubes allow a particular seat adjuster mechanism to be used with seats on different vehicle models. Further, the tubular construction allows cost savings and weight savings over a solid machined rod. Two known prior art jack extension tubes are shown in greater detail in commonly-assigned U.S. Pat. Nos. 5,312,198 and 5,536,100 issued May 17, 1994 and Jul. 16, 1996, respectively. Typically, the link member is mounted to the extension tube by a fastener such as a shoulder bolt with an attached nut, a pin, a rivet and the like.
However, because these extension tubes are often manufactured solely from steel or other metal components, some prior jack extension tubes have been known to make excessive amounts of noise during operationxe2x80x94more than is aesthetically pleasing while adjusting the seat in the passenger compartment of the vehicle. Further, prior extension tubes are often subject to xe2x80x9cchuckingxe2x80x9dxe2x80x94looseness between components of the jack extension tube and adjustment screw which contributes to unacceptable noise and seat vibration. Further, damage can occur between components of the extension tubes as the tube approaches an innermost or outermost position, especially in circumstances where various components are made from different materials having disparate hardness and strength.
The invention generally relates to a jack extension tube for vehicles comprising an elongated tube having a first section with an open end and a second section spaced from the first section. A threaded nut is mounted in the first section and a mounting flange is provided in the second section which is adapted to receive a fastener. A jack screw is received in the first section open end and is threadably received in the threaded nut. The jack screw can include an exposed end defining a gear and an opposite end configured so that the jack screw is retained in the threaded nut and cannot be fully unscrewed from the threaded nut.
In a specific embodiment, the invention comprises a jack extension tube preferably for vehicles is provided which comprises an elongated tube having a first section with an open end and a second section spaced from the first section, the tube made from a first material. A nut made from a second material less rigid than the first material is fixedly mounted in the first section, the nut having first and second opposed faces and a threaded bore therethrough. The threaded bore preferably terminates in the first and second faces of the nut.
Holes are provided in the second section adapted to receive a fastener, a jack screw is received in the first section open end and is threadably received in the threaded bore of the nut. The jack screw has at least one of an exposed end with a gear, an opposite end defining a stop which retains the nut on the jack screw when the nut is threaded to the opposite end of the jack screw, and a gear housing mounted adjacent to the screw.
The jack screw is thereby threadingly mounted for movement between a fully extended and a fully retracted position with respect to the nut. The nut preferably has an extension extending outwardly from each of the first and second faces thereof, the extensions made from a third material less rigid than the first material. The extension on each face of the nut is configured so as to contact the gear hub, the stop, and the gear housing to thereby prevent the screw both from damaging the nut, the stop, and the gear housing into the nut as well as drawing the at least one of the gear, the stop, and the gear housing into the elongated tube as the jack screw approaches the fully extended or fully retracted positions with respect to the nut.
In more specific embodiments of the invention, the third material can be the same as the second material whereby the nut and the extensions are made as a unit from the same material. The stop can be made from the same material as the nut. The at least one of the gear and the gear housing has a portion contacting the nut in the fully retracted position made from the same material as the nut. The housing can comprise at least one punched-in area adjacent either opposed face of the nut to encapsulate retain the nut within the housing and thereby prevent axial movement of the threaded nut within the elongated tube. The second material can comprise rigid synthetic resin material. The first material can comprise one of aluminum, steel and a steel alloy. The second material can be reinforced with fibers. The second material can be a reinforced nylon material. Threads on the threaded bore of the nut can be involute threads.
The fixed mounting of the nut to the tube comprises deformed areas of the elongated tube encapsulating at least a portion of each of the opposed faces of the nut to prevent substantial axial movement of the nut with respect to the elongated tube. At least one of the extensions of the nut extends beyond the deformed areas of the housing whereby the at least one of the extensions form a bearing surface for receiving the at least one of the at least one of the gear, the stop, and the gear housing when the screw approaches the fully extended or fully retracted positions with respect to the nut.